1. Field of the Invention
The present invention relates to an image sensor, and more particularly, to an image sensor which is capable of avoiding light shielding and minimizing hue shift.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 shows a simplified diagram of a conventional image sensor 100. As shown in FIG. 1, the image sensor 100 comprises: pixels 110, 120, 130, and a module lens 140 positioned above the pixels 110, 120, 130. The pixel 110 comprises a photodiode 112 and two dummy metal segments 114. The pixel 120 comprises a photodiode 122 and two dummy metal segments 124. The pixel 130 comprises a photodiode 132 and two dummy metal segments 134. The dummy metal segments 114, 124, 134 are utilized for achieving symmetry for the pixels 110, 120, 130, respectively. However, due to larger chief ray angle (CRA) for the pixels 120, 130 near the edges of the pixel array, light is partially shielded by the dummy metal segments 124, 134, respectively. CRA will be larger when height of the image sensor 100 is further reduced, and the light shielding problem becomes more serious. In addition, hue shift can still exist due to asymmetry of the photodiode or polysilicon shape in the image sensor 100.
Please refer to FIG. 2. FIG. 2 shows a simplified diagram of another conventional image sensor 200 disclosed in U.S. Pat. No. 7,214,920. As shown in FIG. 2, the image sensor 200 comprises: pixels 210, 220, 230, and a light source 240. The pixel 210 comprises a photodiode 212 and two dummy metal segments 214. The pixel 220 comprises a photodiode 222 and two dummy metal segments 224. The pixel 230 comprises a photodiode 232 and two dummy metal segments 234. The light shielding problem is minimized by spatially varied dummy metal segments as shown in FIG. 2, and this variation is made progressively from the center to the edges of the pixel array. However, the metal route positions have to be changed for the variation.